Giant magnetoresistance (GMR) elements and tunneling magnetoresistance (TMR) elements are known as magnetoresistance effect elements. GMR elements are composed of a multi-layer film including a ferromagnetic layer and a nonmagnetic layer. In TMR elements, an insulating layer (tunnel barrier layer, barrier layer) is used as a nonmagnetic layer. Generally, an element resistance of a TMR element is higher than an element resistance of a GMR element. However, a magnetoresistance (MR) ratio of a TMR element is higher than an MR ratio of a GMR element. Magnetoresistance effect elements are being focused on as magnetic sensors, high frequency components, magnetic heads and nonvolatile random access memory (MRAM) elements.
As a writing method for an MRAM, a method of performing writing using a magnetic field caused by a current (using magnetization inversion), a method of performing writing using a spin transfer torque (STT) generated by applying a current in a lamination direction of magnetoresistance elements (using magnetization inversion), and the like are known. In the method of performing writing using a magnetic field, there is a limit to a current that can flow into a thin wiring and there is a risk of writing not being possible when an element size becomes smaller.
On the other hand, in the method of using a spin transfer torque (STT), a current is applied in the lamination direction of the magnetoresistance effect element. A spin-polarized current in one ferromagnetic layer (fixed layer, reference layer) is transferred to the other ferromagnetic layer (free layer, recording layer). According to this transfer, a spin transfer torque (STT) is applied to magnetization of the other ferromagnetic layer (free layer, recording layer), and writing (magnetization inversion) is performed. Therefore, when the element size is smaller, a current required for writing becomes lower, and there is an advantage that integration becomes easier.